Occasionally, people can survive falling large distances if the surface they land on is soft enough. During a traverse of Eiger's infamous Nordvand, mountaineer Carlos Ragone's rock anchor gave way and he plummeted 488 feet to land in snow. Amazingly, he suffered only a few bruises and a wrenched shoulder. Assuming that his impact left a hole in the snow 4.5 ft deep, estimate his average acceleration as he slowed to a stop (that is while he was impacting the snow)

I thought it was -3491.6 m/s^2 which was incorrect please help ASAP. Thanks.